The objectives of this study are to understand the organization of synaptic contacts in the retina and the biochemical mechanisms underlying synaptic neurotransmission. Specific projects presently ongoing or planned for the next five years include: 1) An electron microscopic analysis of the synaptic organization of amino acid-accumulating and peptide-containing amacrine cells in the rabbit retina. 2) A biochemical study of dopamine-dependent adenylate cyclase activity and dopamine-dependent protein phosphorylation in isolated carp horizontal cells. 3) A biochemical study of vasoactive intestinal peptide (VIP) stimulation of cyclic AMP accumulation in the carp retina. 4) A combined anatomical and biochemical study of carp horizontal cells maintained in cell culture. 5) A biochemical study of the properties of the dopamine receptors on isolated carp horizontal cells and the antigenic properties of isolated carp horizontal cells.